Method and means for transmitting electric signals



March #16, 1954 F. H. RAYMOND 2,672,516

METHOD AND MEANS FOR TRANSMITTING ELECTRIC SIGNALS Filed March 3, 1950 I5 Sheets-Sheet l caowo/ PUZ-i 4: Wm; cam me 77 222?! 47 H I I was: GEM

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I 1. was ape-Mme 47 I I .wuss GEM w m6 col/N75 A R W was J/MPEA? March 16, 1954 F. H- RAYMOND METHOD AND MEANS FOR TRANSMITTING ELECTRIC SIGNALS Filed March 3, 1950 3 Sheets-Sheet 3 Patented Mar. 16 1954 UNITED, STAT Es PATENT FFICE...

METHOD AND MEANS For: TRANSMITTING ELECTRIC SIGNALS The present invention relates to a method and means for transmitting electric signals in those types of intelligence transferring systems in which signals from a plurality of individual channels aretransmitted successively over a common transmission channel, and at the receiving station, or any other desired site,are distributed: in turn to theirr'espective individual channels. I In earlier known systems a synchronized timing distributo'r'has been usedat the location where the individual channels and the common transmission line meet, thus introducing a cross talk level between channels too high to'be eliminated, but the present invention dispenses with the timing distributor andtherefore dispenses with the disturbing cross talk.

The'invention relates to systems of -the' above mentioned type in which, threshold circuits, or,

so-called 'gatesfl-are used for opening the indi-' vidual channels in turn to the'common signaltransmission channel, bothat a transmitter and at-a receiving point. The gate for a'givenchannel is normally-biased'to stay'closed until-a gat ing iinpulse of a predetermined amplitude is applied to it to open it for passage-of its proper intelligence signal." Different amplitude levels; are assigned to the gates in; the different indi vidual channels, so that the gates 'are opened in the-order of the amplitude 'levelsp-In' earlier known systems stepped voltages have beerrused to open the-gates in' a predetermined sequencedepending on the consecutive magnitudes ofthe" stepped voltages, but the present-inventionmakes it: possible'to open the gates in any desiredorder instead ofin apredetermined set sequence. That is, this invention gives complete freedom,'when=" ever'this is desired, regarding the transmission" corresponding to the different seduence of signals channels.

The features which make possible the"avoidance of the timing distributor and theflexibility of'channel sequence, are the transmission of a pilot signal before the intelligence signal from" each channel and the application either to the pilot signal itself, "or to the channel intelligence signal itself, of a code that tells what amplitude level voltage will open the proper channel gate. 3

That is, the height of theamplitude level re qu'ired for-opening'the desired gate is expressed, say, in'numerical'code, and this coded number is made a part of the pilot signal or of the intelligence signal of the particular channel whose gate will open at the amplitude level represented by the coded number.

object of the invention, therefore, is to transmitalong with each signal from a particular channel its own pilot signal and a coded indication of the amplitude level at which the channel gate operates.

A corresponding object is to decode at the distribution point, each pilot signal and its associatedlchannel intelligence signal so as to get an indication of the amplitude levelat which'the-f channel gate operates.

apply the coded amplitude level pilot signal.

channel intelligence signal itself.

The invention finds application in multiplex signaling systems including multiplex -commun i-' cation systems of the time-division type'in' which a channel signal may be a series of samples of varying magnitude of the voice wave to be transmitted. The prior art shows that the channel signals of one channel in this case maybe a series'of trains of impulses, each train desigparticular magnitude" nating in numerical code a I oi signal current. The coded channel signal in this case and the coded amplitude level signal telling what channel gate must be opened, may becombined for transmission over the common transmission line for decoding at the distributionpoint.

The invention also finds application in computing networks in which partial calculating results which are the channel signals, stand for mathematical magnitudes; these must be transferred to other places in the calculating machine as a succession of trains of impulses and the] trains must then be distributed so that the mathematical magnitudes may again other calculating channels. I

In multichannel systems of the above-menbe acted on in tioned time division type it is possible to signal by the use of position modulated impulses or by codeimpulses, since only one amplitude serves for the transmission of all'signals. I

The present invention while maintaining'the advantages of the modulation means mentioned, f does'away with inconveniences of previous systems" by assigning as many amplitude" levels there are individual channels, making the'particular amplitude level a characteristic of the than nel, introducing in code an indication of theas' signed amplitude level for each message signal of that channel, decoding said indicationat'the" point of distribution and using the decodedre'-" suit to open passage into the selected channel, and eliminating the amplitude level'indication at" Specifically, It is an object of theinventi'onto' signal to the; Specifically also it is an object to" apply the coded amplitude level signal to the transmission system, which said signals are pre;

coded in amplitude levels according to thepreceding practice. For the sake of simplicity, three channels only are considered, though the possi-,

bility of extension to any greater number of channels is quite plain.

in common by the conductor 49.

"In the arrangement shown in Fig. 3, only two In the arrangement of Fig. 1, the three information signals are brought on the three channels 23, 24, 25 and applied onto tubes tude levels; said arrangement will have its ad- 21, 28; if wanted, a previous amplitudecompression may have taren place so that these signals will have predetermined maximum amplitude levels. Said tubes 25,21, 28. arenormally blocked and are unblocked in sequence by timing impulses applied through wires 29,30 'and' 3| onto for example, their screen-grids. The outputs of these tubes are connected in common, througha delaying line .(such as an artificial line, section) 32 to an encoder device 33' which cone verts each amplitude modulated impulse,-,into

acoded impulse train. r p

Further, each timing impulse is re pectively applied onto anencoder 34; 35,.or ,3fi.,-for. instance of the type. described in French Patent- No. 988,021 which converts it into a coded pulse train carrying the level amplitude ofpthe .channel .to which said .monitor impulse is related Each monitor signal thus. coded, shall; be apr plied onto the common transmission conductor 31 through suitable dimensioning of the delaying line-.32, beforeeach-information coded signal the said information signal.

Theoperation process is analogous inFig. 2,-

but in said arrangement, the coded trainoi im-. pulses representing the predetermined ampli- 26 tov 28. includes a branch circuit which, as

shown in 38,, 39, 40,. reads the codes applied to encoding. quadripoles 34,. 35, 35. The coded trains thus derived are added, at sLbymixing and at a predetermined interval withrespect t followed by rectification through a carry-over operator at 43, to s the amplitude-modulated pulses fromtubes 26, 21, 28. As analternative,

thefquadripoles 34 to 35 may be. replaced by amplitude encoders and theprocess of rectificaev tion bycarry-over established at '43 ensures atrain of impulses coded both in response to the amplitude of, the information signal and the amplitude level of its corresponding channeh Connections linking the outputs of tubes 25 to 28, to encoders 34to 36, areone way as indicated at 44,455 and 46, in order to avoid undue inter-.

ferences between channel outputs.

In, Fig. 2, also, is indicated a"preferred ar-f rangement for producing the monitor pulses: it

comprises an impulse generator 41which delivers itsim pulses at the input of a ringcounter,

I lI 'I I I, in cascade'connection closed by a one I way feedback 48. Theoutput pulses of these, stagesareapplied on one hand, onto, scree gridsof tubes 25to 28,, and onthe othen lonto a shaping circuit 50 which apply to theme char-91 acteristicconformation before delivering the said,

reshaped pulses to the outputtransmission service way 31, in order that each. monitor signal should precede its corresponding information/ amplitude level signaldelayed at 32., ,i

' channel tubes 25,

vthe other delayed from 6, and both feeding the service way 31 in the same way as they are fed encoders are provided for producing the pulse coded trains carrying the predetermined amplivantage in multiplex transmission systems of a relatively high number of channels. These two encoders are indicated at 5| and 52. The encoder 5| receives every output signal of the and is adjusted to supply to the delaying line 32, a train of pulses coded with the lower amplitude level, e. g., the channel No. 1; encoder 52 corresponds to the producing of a pulse train coded at an arbitrary level amplitude and its output is connected to that of encoder 5|. Its input, however, is fed by signals resulting from the delay in the circuits, as indicated at 53, 54, of outputs of the other channel tubes; and said delay circuits (artificial line sections) present increasing delay values as they are fed by channel tubes of higher rank in the considered group. Hence, said encoder, 52, when energized by the tube of the second channel, will deliver a pulse signal (a single pulse may be sufiicient) which is taken as a signal of order 2 -with respect to the signal put forth by encoder mathematical meaning of the word when considering the numerical development of any number with respect to a definite radix of numeration.

By said arrangement, any amplitude level relative to any channel is produced in the form of acoded pulse train, as a result of the described association of the two encoders 5|--52 and the associated delaying lines 53, 54.

In any multiplex transmission system, and especially, if the number of channels is great it ,is. desirable to transmit only those effective signals which. appear in the various channels and to. omit those of said channels which are uneffective at any time. The provision of the method of transmission according to the present invention enables such a kind of operation since 'itis no longer a prerequisite condition to maintain,fixed recurrence in the sequence of transmission of said chamiels.

Fig 4. shows a simple way of obtaining such a selection, in which passing-through from an active,. channel to another active channel is ensured, however many intermediatechannels may be inactive at the time concerned.

To this purpose, each of the incoming channels '23, is provided wtih a signal detector 55,56, 57 i. e.made of a full-wave rectifier, the output of which acts when activated, one. relay 58, 59, These relays however shown as electro-mechanical relays, will in practice be valves. or,.tube5.,or better flip-flop stages. When therela'y is excited each operating 'contact,"ef-i 23 andi l are not operative (Figure 12) thecounterstage I delivering impulses is connected by means of the rest contacts of relays lia and 59 onto'the'tub'e 25 which will be 'unblockedby' the first impulse; when the second impulse will take place, said tube will again be unblocked by the relay rest contact, and unblocked. again by the thirdimpulse by the operating contact of its own relay. When no information signals appear on channels 23 and'Z i, the information signal from channel 25' will be permanently ana -1' lysed and sampled for transmission. However, thetransmitted signals will always becoded according to the amplitude level relative to said;

third'channel, as said signals will permanently be produced by the delaying line 55 and encoders El and 52 as explained with respect to the arrangement of Fig. 3 reproduced in Fig. 4.

More detailed arrangementsv are shown, in electronical. arrangements, in Figs; 5 and 6, mainly for explaining what is meant hereinbefore by threshold and amplitude band-pass circuits, as well as to state the separation circuit for the monitor signals.

Fig. 5 shows a system in which the pulses are distributed to their respective channels by means of differential amplitude discriminators 88-405 of well known type. 1

The purpose of the decoding device is to give to the message signal the level, which corresponds to the'channel .alongwhich the message is to be directed. The indication of that level is given by the amplitude of the signal which can precede the message signal or be superposed on it. Therefore, at W in Fig. ,5 is obtained the message signal with a predetermined amplitude and the problem is'to separate the N levels, assigned'to the N channels;

For this purpose, each channel is characterized by an amplitude gate of lib- E1, and the device performing the discrimination is shown at Fig. 5 from reference $3 to reference I05.

After the signals pass through the coil 88, a sinusoidal modulation is superposed upon the impulses by source 90 acting through transformer windings 89 and 9!; the amplitude of this modulation being possibly less than, or at the most equal to the width of the gate E's-E1. Therefore, at point 92, the various signals come in with diiferent amplitudes according to the various channels. For example, the signal for channel 1Vpl may have an amplitude less than E1; the signal for channel N p an amplitude between E1 and E2, and the signal for channel N-p-l-l an amplitude greater than E2.

At the point 92 are connected in parallel two rectifiers 94 and 95, polarized by the voltages E2 and E1. The unit is looped on a transformer I62, the primary winding of which has its middle tap grounded and the secondary winding of which is tuned to the frequency of the sinusoidal wave superposed on the impulses.

When signals of the type Np-l come in at 92, the rectifiers 94 and 95 are non-conductive and present a high series impedance in bridges 95-91 and e499. Therefore, no signal is transmitted to transformer l 02.

- When-signals of the type N-p come'inion 'the contrary, rectifier 9511s conductive andallows the passage of the wave train superposed'onthe impulse; the wave may be found again atpoint I05, amplified by the tuned circuit.

After detection, the'message signal is found again and may be decoded and sent into th'eIcor--= responding Np channel. When signals of type N -p+1 come The result is the chocking or blocking of .-the messagesignal in channel Np+1, for example. In this way, the amplitude assigned to channelN-p has been selected'and' the information.

has been'i'sent along the channel corresponding tothat amplitude.

In thealternative embodiment shown in Fig. 6, the monitor signal energizes a sharp parabolic generator 8?. being used, as before, to produce'in' duration the decoded information signal. The

two' voltages thus produced are applied onto a. device 83 such as a flip-flop circuit; the fore-'- front of the information signal, appearing as an amplitude-modulated pulse, produces" a pulse,

when the potentials of said information pulse. and said sharp wave are equal; they annuleach other and produce repeatedoperation of the flip-k; flop 33, hence a second pulse 'is producedthe, time interval of which, depends uponthe ampulse, or is closely.

plitude of said information val or separation of whichis a measure of the magnitude of the carried information, is parallel applied onto the selection parallel ways including each threshold circuits (such as shown by. the

diode tubes 84, biassed' at 85); Each ofv these. channels includes in fact, at its input,a circuit. for coincidence selection, as shown at 86-81,.

identical to the coincidence circuit til-62 of :Fig.

5 but in which the delaying line section 8'! is es? tablished relatively to the various amplitude-lev e els characterizing the various transmission chanof the time division type in which intelligence signals transmitted over a common channel are selectively distributed into a plurality of individual channels, comprising means for producing pilot signals and inserting them between the intelligence signals in said common channel so that each pilot signal is adjacent in time to a corresponding intelligence signal, means at the distribution point for generating a plurality of different amplitude-level voltages one for each channel, normally closed gating means for the individual channels selectively responsive to said different amplitude-level voltages to open the respective channels, means under control of said pilot signals and their associated time-adjacent intelligence signals for selecting said amplitudelevel voltages to open said gating means.

2. A multiplex intelligence transmission system of the time division type in which intelligence signals transmitted over a common channel are selectively distributed into a plurality of individual channels, comprising means for producing pilot signals and inserting them between the intelligence signals in said common channel so that each pilot signal is adjacent in time to a correin, the rectifiers 9A and 95 are conductive, and at the ter minals of condensers I90 and [0| are found twoidentical signals, the action of which is nilzupon the'secondary winding of the transformer I02;

spending intelligence signal, means at the distribution point for generating a plurality of difierent amplitude-level voltages one for each channel, normally closed gating means for the individual channels selectively responsive to said different amplitude-level voltages to open the respective channels, means for coding said pilot signals to select the amplitude-level voltages corresponding to the channels to which theiradjacent intelligence signals are to be distributed, and means under the combined eiiectof said coded pilot signals, said intelligence signals and said selected amplitude-level voltages for selectively opening said gating means.

3. A multiplex intelligence transmission system of the time division type in which intelligence signals transmitted over a common channel are selectively distributed into a plurality of individual channels, comprising means for producing pilot signals and inserting them between the intelligence signals in said common channel so that each pilot signal is adjacent in time to a corresponding intelligence signal, means at the distribution point for generating a plurality of different amplitude-level voltages one for each channel, normally closed gating means for the individual channels selectively responsive to said different amplitude-level voltages to open the respective channels, means for coding said pilot signals to indicate for each pilot signal the amplitude-level voltage corresponding to the channel to which the adjacent intelligence signal is to be distributed, means for decoding said pilot signals at the distribution point to derive the indicated amplitude-level voltage, and means for adding the derived amplitude-level voltage to the associated intelligence signal, for operation of the appropriate gating means.

4. A multiplex intelligence transmission system of the time division type in which intelligence signals transmitted over a common channel are selectively distributed into a plurality of individual channels, comprising means for producing pilot signals and inserting them between the intelligence signals in said common channel so that each pilot signal is adjacent in time to a corresponding intelligence signal, means at the distribution point for generating a plurality of different amplitude-level voltages one for each channel, normally closed gating means for the individual channels selectively responsive to said different amplitude-level voltages to open the respective channels, means for coding said intelligence signals to select the amplitude-level voltages corresponding to the channels to which said intelligence signals are to be distributed, and means under the combined effect of said coded intelligence signals, said pilot signals and said selected amplitude-level voltages for selectively opening said gating means.

5. A multiplex intelligence transmission system of the time division type in which intelligence signals transmitted over a common channel are selectively distributed into a plurality of individual channels, comprising means for producing pilot signals and inserting them between the intelligence signals in said common channel so that each pilot signal is adjacent in time to a corresponding intelligence signal, means at the distribution point for generating a plurality of difierent amplitude-level voltages one for each channel, normally closed gating means for the individual channels selectively responsive to said different amplitude-level voltages to open the respective channels, means for coding said intelligence signals to indicate for each intelligence signal the amplitude-level voltage corresponding to the channel to which the adjacent intelligence signal is to be distributed, means for decoding said intelligence signals at the distribution point to derive the indicated amplitude-level voltage, and means for adding the derived amplitude-level voltage signal to the associated intelligence signal for operation of the appropriate gating means.

FRANCOIS HENRI RAYMOND.

Number Name Date 2,543,738 Houghton Feb. 27, 1951 Houghton Nov. 28, 1950' 

